Device for supplying current to the bottom of electrolytic furnaces



Jan. 13, 1959 v P. PONTREMOLI DEVICE FOR SUPPLYING CURRENT TO THE BOTTOMOF ELECTROLYTIC FURNACES 2 Sheets-Sheet 1 Filed Nov. 10, 1954 INVENTOR.

Jan. 13, 1959 P. PONTREMOIII 2,868,710

DEVICE FOR SUPPLYING CURRENT TO THE BOTTOM 7 OF ELECTROLYTIC FURNACES 2Sheets-Sheet 2 Filed NOV. 10, 1954 Fig. 2b

Fig.2c

INVEN TOR.

, 6%. (PM 7 BY United States Patent DEVICE FOR SUPPLYING CURRENT TO THEBOTTOM OF ELECTROLYTIC FURNACES Pio Pontremoli, Milan, Italy, assignorto Montecatini Societa Generale per llndustria Mineraria e Chimica,Milan, Italy, a corporation of Italy Application November 10, 1954-,Serial No. 468,120

Claims priority, application Italy November 17, 1952 Claims. (Cl.204-243) because the current has the tendency to distribute itselfirregularly over the individual areas of the bottom regardless ofwhether the bottom is composed of carbon blocks or of tamped carbonpaste or compound.

A uniform current distribution and density in the cathodic bottom of analuminum furnace, however, is desirable for attaining optimum durabilityof the bottom structure itself and for securing most favorableconsumption of the anode or anodes above the furnace bottom. The furnacebottom represents a large proportion in cost of the entire furnace; andonly by avoiding the occurrence of current concentrations at singularpoints and thus local overheating of the bottom can optimum life of thebottom and maximum regularity and economy of furnace operation beachieved.

It is an object of my invention, therefore, to improve thecurrent-supply devices so as to secure a virtually perfect uniformity ofcurrent density in the furnace bottom without appreciable complicationin furnace design and without entailing the increased susceptibility toinjurious ingress of airv encountered with past attempts at improvingcurrent distribution. It is another, more specific object of myinvention, to secure the desired uniformity of cur rent distributionwith the aid of a horizontal arrangement of cathode conductors enteringfrom the side into the furnace bottom.

This and more specific objects of my invention as well as the means forachieving them will be apparent from the following description taken inconjunction with the drawings in which;

Figs. la and lb show a longitudinal section and cross sectionrespectively of a furnace bottom portion according to the invention, andFigs. 1c and ld are coordinate. diagrams of current distribution;

Fig. 2a is a longitudinal section through a bottom portion according toanother embodiment of the invention, and Figs. 2b and 2c are explanatorydiagrams of current distribution curves.

Fig. 3 is a vertical longitudinal section through a furnace embodyingthe device of Fig. 2a.

In Figs. 1a, 1b and in Fig. 2a, the layer of molten aluminum is denotedby 11, while 12 denotes a portion of the furnace bottom consisting of ablock or a tamped mass of carbon material. Embedded in the bottomportion are a cathode conductor 13 of iron and a bus bar 14. Accordingto Fig. la, the bus bar is connected with the cathode conductor in asingle central zone of the latter and may form an integral piecetogether with the conductor. In the embodiment of Fig. 2a, the bus bar14 is joined with the cathode conductor 13 in two zones longitudinallyspaced from each other. Depending upon the length of ice 2 the furnacebottom in the direction of the bus bars, more than two junction zonesmaybe provided.

If desired, each bus bar 14 and each connecting zone may be electricallyinsulated from the carbon material of thefurnace bottom, as shown at 17in Figs. 1a, lb and 2a, to prevent a direct passage oflcurrent from thebus bar to the cathodic bottom. The insulation 17 may consist of a sheetof asbestos, a layer of heat-proof cement, mica or any other insulatingmaterial resistant to temperaturesof 800 C. or more.

The current distribution within the carbonaceous furnace bottom abovethe cathode conductor is in accordance with curves 15 in the diagrams ofFigs. 1d and 2c. The current distribution at the contact surface betweenfurnace bottom and molten aluminum is as shown by curve 16 in Figs. 1cand 2b.

As these diagrams show, an excellent uniformity of current distributionand current density is secured and, as mentioned, a further improvementin this respect can be obtained by providing more than two junctionzones suitably spaced from each other.

In a cathode and bus bar system according to the invention, the bus barsof the furnace bottom extend all to the side of the bottom so that it isunnecessary to resort to special and cumbersome expedients for securinga reliable sealing against ingress of air.

Fig. 3 illustrates a furnace or cell for production of aluminum,employing the cathode structure 13, 14, 17 of Fig. 2a. At 20 is theconventional anode, usually of carbonaceous material. The anode isordinarily movably supported, for upward and downward motion, and hasiron conductor rods 21', 22 embedded therein.

I claim:

l'. A molten bath furnace for igneous electrolysis of aluminum,comprising a cathodic bottom portion supporting the molten bath and aconsumable anode above the bottom portion, thebottom portion comprisinga block of carbonaceous material having a horizontal top surface forcontact with the aluminum and having a bottom surface and' lateral sidesurfaces, a cathode conductor of metal fully embedded in said materialand extending parallelto said top surface, a bus bar-of metal laterallyextending from the outside through one of said side surfaces to withinsaid block and being located beneath said cathode conductor and adjacentto said bottom surface in parallel and spaced relation to saidconductor, the bus bar being enclosed in the carbonaceous block at itsupper face, the lower face of the bar being exposed along the bottomsurface of the block, and connecting means joining said bus bar withsaid cathode conductor within said bottom portion and extending upwardlybetween said bar and conductor in spaced relation from the ends of saidconductor, said connecting means being integrally formed with said busbar and conductor, whereby the conductor is supported by the bus bar andthe current from said bus bar is uniformly distributed from said cathodeconductor through said carbonaceous material to said top surface.

2. A molten bath furnace for igneous electrolysis of aluminum,comprising a cathodic bottom portion supporting the molten bath and aconsumable anode above the bottom portion, the bottom portion comprisinga block of carbonaceous material having a horizontal top surface forcontact with the aluminum and having a bottom surface and lateral sidesurfaces, a cathode conductor of metal fully embedded in said materialand extending parallel to said top surface, a bus bar of metal laterallyextending from the outside through one of said side surfaces to withinsaid block and being located beneath said cathode conductor and adjacentto said bottom surface in parallel and spaced relation to saidconductor, .the bus bar being enclosed in the carbonaceous block at itsupper face, the lower face of the bar being exposed along the bottomsurface of the block, and a plurality of connecting sections spacedlengthwise of and joining said bus bar with said cathode conductorwithinsaid bottom portion and extending upwardly between said bar andconductor in spaced relation from the ends of said conductor, saidconnecting means being integrally joined with said bus bar andconductor, whereby the conductor is supported by the bus bar and thecurrent from said bus bar is uniformly distributed from said cathodeconductor through said carbonaceous material to said top surface.

' 3. A molten bath furnace for igneous electrolysis of aluminum,comprising a cathodic bottom portion supporting the molten bath and aconsumable anode above the bottom portion, the bottom portion comprisinga block of carbonaceous material having a horizontal top surface forcontact with the aluminum and having a bottom surface and lateral sidesurfaces, a cathode conductor of metal fully embedded in said materialand extending parallel to said top surface, a bus bar of metal laterallyextending from the outside through one of said side surfaces to withinsaid block and being located beneath said cathode conductor and adjacentto said bottom surface in parallel and spaced relation to saidconductor, the bus bar being enclosed in the carbonaceous block at itsupper face, the lower face of the bar being exposed along the bottomsurface of the block, and connecting means joining said bus bar withsaid cathode conductor within said bottom portion and extendingvertically between said bar and conductor in centrally spaced relationfrom the ends of said conductor, said connecting means benig integrallyjoined with said bus bar and conductor, whereby the current from saidbus bar is uniformly distributed from said cathode conductor throughsaid carbonaceous material to said top surface.

4. A furnace for igneous electrolysis of a molten bath, comprising acathodic bottom portion supporting the molten bath and a consumableanode above the bottom portion, the bottom portion comprising a mass ofelectroconductive material having a top surface for contact with themolten bath and having a bottom surface and lateral side surfaces, acathode conductor of metal fully embedded in said material and extendingparallel to said top surface, a bus bar of metal laterally extendingfrom the outside through one of said side surface to within said massand being located beneath said cathode conductor and adjacent to saidbottom surface in parallel and spaced relation to said conductor, thebus bar being enclosed in the said mass at its upper face, the lowerface of the bar being exposed along the bottom surface of the mass, andconnecting means joining said bus bar with said cathode conductor withinsaid bottom portion and extending upwardly between'said bar andconductor in symmetrically spaced relation from the ends of saidconductor, said connecting means being integrally joined with said busbar and conductor, whereby the current from said bus bar is uniformlydistributed from said cathode conductor through said electroconductivematerial to said top surface.

5. An electric furnace for molten materials, comprising an electrodicbottom portion supporting the molten material, the bottom portioncomprising a mass of electroconductive material having a horizontal topsurface for contact with the aluminum and having a bottom surface andlateral side surfaces, a metal conductor fully embedded in saidelectroconductive material and extending parallel to said top surface, abus bar of metal laterally extending from the outsidethrough one of saidside surfaces to within said mass and being located beneath saidconductor and adjacent to said bottom surface in parallel and spacedrelation to said conductor, the bus bar being v enclosed in the saidmass at its upper face and along the sides, the lower face of the barbeing exposed along the bottom surface of the mass, and connecting meansjoining said bus bar with said conductor within said bottom portion andextending upwardly between said bar and conductor in symmetricallyspaced relation from the ends of said conductor, said connecting meansbeing integrally joined with said bus bar and conductor, whereby theconductor is supported by the bus bar and the current from said bus baris uniformly distributed from said conductor through said carbonaceousmaterial to said topsurface.

References Cited in the file of this patent UNITED STATES PATENTS2,331,320 Hartzell Oct. 12, 1943 2,528,905 Ollivier Nov. 7, 1950 FOREIGNPATENTS 871,497 France Jan. 17, 1942 1,052,106 France Sept. 23, 1953UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO.2,868,710 January 13 95 Pio Pontremoli rs in the above numbered It ishereby certified that error appea patent requiring correction and thatthe said Letters Patent should read as corrected below In the heading tothe printed specification, line 8, for the priority date November 17,1952" read November 17, 1953 ===u Signed and sealed this 21st day ofApril 195% (SEAL) Attest:

KARL Ho AXLINE ROBERT c. WATSON Conmissioner of Patents AttestingOfficer

1. A MOLTEN BATH FURNACE FOR IGNEOUS ELECTROLYSIS OF ALUMINUM,COMPRISING A CATHODIC BOTTOM PORTION SUPPORTING THE MOLTEN BATH AND ACONSUMABLE ANODE ABOVE THE BOTTOM PORTION, THE BOTTOM PORTION COMPRISINGA BLOCK OF CARBONACEOUS MATERIAL HAVING A HORIZONTAL TOP SURFACE FORCONTACT WITH THE ALUMINUM AND HAVING A BOTTOM SURFACE AND LATERAL SIDESURFACE, A CATHODE CONDUCTOR OF METAL FULLY EMBEDDED IN SAID MATERIALAND EXTENDING PARALLEL TO SAID TOP SURFACE, A BUS BAR OF METAL LATERALLYEXTENDING FROM THE OUTSIDE THROUGH ONE OF SAID SIDE SURFACES TO WITHINSAID BLOCK AND BEING LOCATED BENEATH SAID CATHODE CONDUCTOR AND ADJACENTTO SAID BOTTOM SURFACE IN PARALLEL AND SPACED RELATION TO SAIDCONDUCTOR, THE BUS BAR BEING ENCLOSED IN THE CARBONACEOUS BLOCK AT ITSUPPER FACE, THE LOWER FACE OF THE BAR BEING EXPOSED ALONG THE BOTTOMSURFACE OF THE BLOCK, AND CONNECTING MEANS JOINING SAID BUS BAR WITHSAID CATHODE CONDUCTOR WITHIN SAID BOTTOM PORTION AND EXTENDING UPWARDLYBETWEEN SAID BAR AND CONDUCTOR IN SPACED RELATION FROM THE ENDS OF SAIDCONDUCTOR, SAID CONNECTING MEANS BEING INTEGRALLY FORMED WITH SAID BUSBAR AND CONDUCTOR, WHEREBY THE CONDUCTOR IS SUPPORTED BY THE BUS BAR ANDTHE CURRENT FROM SAID BUS BAR IS UNIFORMLY DISTRIBUTED FROM SAID CATHODECONDUCTOR THROUGH SAID CARBONACEOUS MATERIAL TO SAID TOP SURFACE.